The United Nations Security Council Tuesday voted unanimously to extend the mandate of a U.N. observer force in the contested Western Sahara, but failed to agree on the political future of the territory.

Security Council diplomats remain divided on how to end the long-standing dispute over Western Sahara's political future. The options are for the territory to remain a part of Morocco or be granted a referendum on independence.

The resolution gives the more than 200-member peacekeeping force another six months, until the end of January. In the meantime, it calls on Secretary-General Kofi Annan and his personal envoy for Western Sahara, former U.S. Secretary of State James Baker, to continue their efforts to find a way out of the political impasse.

Mr. Baker is believed to favor keeping Western Sahara as part of Morocco, though with substantial autonomy. France, Britain and the United States lean in that direction. But other governments on the Security Council want a referendum to give the residents of Western Sahara the choice of total independence.

Security Council president Jeremy Greenstock of Britain suggested the compromise resolution gives everybody more time. "It has the support I understand, or at least the condonement, of the parties," he said. "And therefore, I hope that will provide a good foundation for further work by the personal envoy to try to bring this long-standing dispute to an end, or at least to make progress in the political negotiations that we have now asked for."

Morocco annexed the former Spanish colony after Spain withdrew in 1975. This was followed by 15 years of a guerrilla war with the Polisario Front, a group dedicated to the territory's independence. The United Nations itself endorsed a referendum in 1991. But efforts to organize one have been bogged down in disagreement over who is eligible to vote.